The purpose of this proposal is to request partial support for a workshop on the pathogenesis of non-acute retroviruses. Viruses to be considered include the murine leukemia, avian leukosis, feline leukemia, and murine mammary tumor viruses. Areas to be covered include viral and host genetics, and the molecular biology, and immunology of the disease process. A similar, highly successful meeting had been previously organized by Drs. Hung Y. Fan and Maxine Linial on December 1-4,1988. Given the progress made during the last two years in this very important area of research, we consider it timely to reconvene the group for another in-depth workshop. Projected attendance is 150 individuals.